Molecular differentiation of coagulase-positive staphylococcal isolates carrying mecA- and PVL-encoding genes among healthy males

Abstract

Aims: This study was aimed to monitor the asymptomatic carriage of coagulase-positive staphylococcal bacteria among university male students and detect the prevalence of virulence marker genes that encode methicillin resistance (mecA) and Panton-Valentine leukocidin (PVL) toxin among the isolates. Methodology and results: Single nasal swaps were collected from 144 participating students who resided at four different locations within Al-Madinah city. A total of 112 Gram-positive staphylococcal isolates were recovered from the 144 participants (carriage rate of 77.8%). Coagulase-positive staphylococci were differentiated using duplex PCR amplification of the 16S rRNA and nuc genes and accounted for 30 isolates (carriage rate of 20.8%). These isolates were most prevalent in the northern and southern parts of Al-Madinah city, while the lowest numbers of isolates were detected in students of the eastern part. Coagulase-positive isolates were further phenotypically characterized for methicillin resistance by the disc diffusion method. Uniplex PCR assays were conducted to screen for mecA-and PVL toxin-encoding genes. The mecA gene was amplified from all 15 (50%) methicillin-resistant coagulase-positive isolates, while the PVL toxin-encoding gene was detected in 19 isolates (63.3%), 10 (33.3%) of which contained the mecA gene. Lastly, PCR amplification of the NRPS gene from coagulase-positive isolates revealed the absence of Staphylococcus argenteus, the recently discovered genetically divergent lineage of Staphylococcus aureus. Conclusion, significance and impact of study: An elevated prevalence of coagulase-positive isolates harboring mecA and PVL virulence genes was observed compared with previous investigations. This poses a potential threat if they spread among the population, resulting in outbreaks of community-acquired infections.